How would I make these curved indents in this water bottle? Picture in description.
Start by making the main outline of your bottle. Once you have that, hover over the section you want to add the inset to and press Ctrl+R. Use the scroll wheel to select exactly how many you want.

Now use Ctrl+Tab+E to switch to edge select mode. Holding Alt+Shift, right click on the newly added loop-cuts. Press Ctrl+B to bevel and roll the scroll wheel one click to add another loop cut in the middle.

Now select the inner loop-cut on each of those rings. Now press Ctrl+. (period) to change to the Individual Origins pivot point. Scale the selection down as desired.

Now go into orthographic mode, and press Numpad 1 and select the center vertices as shown. Move them up as desired. Go ahead and press Numpad 3 and do the same thing. Enable a Subdivision Modifier, and bevel the edges using Ctrl+B.


Final result: